Shabbir Muhammad Waqas, Leuenberger Michael N
NanoScience Technology Center and Department of Physics, University of Central Florida, Orlando, FL, 32826, USA.
College of Optics and Photonics, University of Central Florida, Orlando, FL, 32826, USA.
Sci Rep. 2020 Oct 16;10(1):17540. doi: 10.1038/s41598-020-73582-3.
We present a proof of concept for a spectrally selective thermal mid-IR source based on nanopatterned graphene (NPG) with a typical mobility of CVD-grown graphene (up to 3000 [Formula: see text]), ensuring scalability to large areas. For that, we solve the electrostatic problem of a conducting hyperboloid with an elliptical wormhole in the presence of an in-plane electric field. The localized surface plasmons (LSPs) on the NPG sheet, partially hybridized with graphene phonons and surface phonons of the neighboring materials, allow for the control and tuning of the thermal emission spectrum in the wavelength regime from [Formula: see text] to 12 [Formula: see text]m by adjusting the size of and distance between the circular holes in a hexagonal or square lattice structure. Most importantly, the LSPs along with an optical cavity increase the emittance of graphene from about 2.3% for pristine graphene to 80% for NPG, thereby outperforming state-of-the-art pristine graphene light sources operating in the near-infrared by at least a factor of 100. According to our COMSOL calculations, a maximum emission power per area of [Formula: see text] W/[Formula: see text] at [Formula: see text] K for a bias voltage of [Formula: see text] V is achieved by controlling the temperature of the hot electrons through the Joule heating. By generalizing Planck's theory to any grey body and deriving the completely general nonlocal fluctuation-dissipation theorem with nonlocal response of surface plasmons in the random phase approximation, we show that the coherence length of the graphene plasmons and the thermally emitted photons can be as large as 13 [Formula: see text]m and 150 [Formula: see text]m, respectively, providing the opportunity to create phased arrays made of nanoantennas represented by the holes in NPG. The spatial phase variation of the coherence allows for beamsteering of the thermal emission in the range between [Formula: see text] and [Formula: see text] by tuning the Fermi energy between [Formula: see text] eV and [Formula: see text] eV through the gate voltage. Our analysis of the nonlocal hydrodynamic response leads to the conjecture that the diffusion length and viscosity in graphene are frequency-dependent. Using finite-difference time domain calculations, coupled mode theory, and RPA, we develop the model of a mid-IR light source based on NPG, which will pave the way to graphene-based optical mid-IR communication, mid-IR color displays, mid-IR spectroscopy, and virus detection.
我们展示了一种基于纳米图案化石墨烯（NPG）的光谱选择性热中红外源的概念验证，该石墨烯具有化学气相沉积生长石墨烯的典型迁移率（高达3000 [公式：见正文]），确保了可扩展到大面积。为此，我们解决了在平面内电场存在下带有椭圆形虫洞的导电双曲面的静电问题。NPG片上的局域表面等离子体激元（LSPs）与石墨烯声子和相邻材料的表面声子部分杂交，通过调整六边形或正方形晶格结构中圆孔的尺寸和间距，可在波长范围从[公式：见正文]至12 [公式：见正文]米内控制和调节热发射光谱。最重要的是，LSPs与光学腔一起将石墨烯的发射率从原始石墨烯的约2.3%提高到NPG的80%，从而使在近红外工作的最先进的原始石墨烯光源的性能至少提高100倍。根据我们的COMSOL计算，通过焦耳加热控制热电子的温度，在[公式：见正文]V的偏置电压下，在[公式：见正文]K时实现了每面积[公式：见正文]W/[公式：见正文]的最大发射功率。通过将普朗克理论推广到任何灰体，并在随机相位近似下推导具有表面等离子体激元非局部响应的完全通用的非局部涨落耗散定理，我们表明石墨烯等离子体激元和热发射光子的相干长度分别可高达13 [公式：见正文]米和150 [公式：见正文]米，这为创建由NPG中的孔所代表的纳米天线组成的相控阵提供了机会。相干性的空间相位变化允许通过栅极电压在[公式：见正文]eV和[公式：见正文]eV之间调节费米能量，从而在[公式：见正文]和[公式：见正文]之间的范围内对热发射进行光束转向。我们对非局部流体动力学响应的分析得出推测，即石墨烯中的扩散长度和粘度与频率有关。使用时域有限差分计算、耦合模理论和随机相位近似，我们开发了基于NPG的中红外光源模型，这将为基于石墨烯的光学中红外通信、中红外彩色显示器、中红外光谱学和病毒检测铺平道路。
